Chapter 2: Group Consensus



  • What are the key chapter elements (take home messages) that I should test you on?



  • What new things are you curious about and/or did not fully understand



  • What is the coolest thing you learned?

We are on leading edge of the space time continuum

How do you view the timeline of the history of life on Earth?


  • Starts at early life?
    • where is that?


  • Biased towards human existence?


  • What processes are key? Is tempo (time between events) important?


  • Something non-science based?


  • Perspective matters: Understanding the history of biodiversity and critical landmarks in life on Earth help us analyze current changes on Earth.

The Earth is old…and it took a while for life to form.

  • Surface was way too hot to start
    • cooled enough to make a solid crust
    • cooled enough sustain liquid water


  • An atmosphere needed to form
    • Without an ozone layer, radiation from sun was too intense
    • Oxygen needed to accumulate for animals


  • Lots of inorganic molecules but no organic molecules
    • early atmosphere was reducing

Miller & Urey experiments: Testing Oparin & Haldane

Origin of herdity was key for contempoary life

  • RNA probably came first
    • ~3.8 billion years ago


  • Somewhere between the formation of RNA and cellular life a mechanisms to pass genetic information from partent to offspring emerged (heredity)


  • Heredity is the key for evolution of life and biodiversity
    • replication → variation → competition → natural selection
    • mutations (replication mistakes) are the unit of variation


  • Heredity likely took place in early ‘protocells’ with compartmentalized RNA
    • have not been re-created in the lab

Cellular life begins ~1 billion years ago

  • “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground.” published by Arrhenius in 1895 while studying ice ages
    • argued that variations in trace atmosphere components (CO2) could greatly influence the heat budget of the Earth
    • Later, he published equations and argued that burning fossil fuels could impact surface temperature


  • Alexander von Humboldt noted that areas surrounding land transformed by agriculture had altered climate (late 1800’s)


  • Guy Callendar published first data linking CO2 and surfaces temperatures in 1938


  • Soon after, studies of the biological impacts of environmental change exploded

What does the field of GCB look like now?



  • Scientific publications are the building blocks of science


  • GCB studies are a key component of the permanent wall of science
    • Now dedicated journals to the field
    • Several high impact journals (Global Change Biology, Nature Climate Change)
    • dedicated books and textbooks


  • Note: communicating science outside of formal publishing is essential
    • indigenous ecological knowledge

GCB scientists face/d an uphill battle

GCB science is interdisciplinary by necessity


GCB embraces diverse perspectives by necessity

Scientific bias in GCB can have vast socio-economic consequences

Targes, investment, policy and consequences do not align

GCB is diverse but utilizes same scientific principles


  • Vast array of methods due to diversity of fields
    • ecology, evolution, conservation, physiology, etc.


  • Data generated is super diverse
    • observational study → genomics → climate modeling


  • Stressors to be studied are many


  • Time frames needed are not the same
  • All these studies utilize the same design principles
    • Independent and dependent variables
    • Treatments and controls
    • Main effects and interactions


  • Studies must have replication
    • modeling or genomics may be exceptions


  • Studies should have randomization

Review and critical thinking of experimental design



Simply define independent and dependent variables


Why is a control treatment absolutely necessary?


Why does replication matter for statistics?


If there is an interaction effect between 2 variables (say warming and drought) are you allowed to talk about a main effect by itself (say warming)?

GCB science varies in approach

  • Observe and record natural systems undergoing change without manipulation
    • tuskless elephants, length of butterfly tongues, etc.


  • Search for mechanisms by manipulation (treatments)
    • field or laboratory
    • focus on key variables


  • Use math and computers to predict
    • use measured trends to project forward with some level of uncertainity
    • species interactions to global climate


  • Combine many single studies to understand if broad patterns exist
    • may ignore unexpected or negative results


  • Use citizen participation to increase scope

GCB science uses the entire cool science toolkit


  • Environmental monitoring must be expansive
    • ocean → atmosphere &#859
    • satellites → lasers → submarines


  • Lots of different organisms to monitor

    • microbes → plants → whales
    • human observation → satellites


  • Biodiversity and species responses are key

    • soil microbiome → adaptation → allele diversity
    • molecular biology tools are vital


  • Many experiments or approached generate large datasets
    • climate monitoring to genomics
    • advanced computing is often necessary


How is GCB data often visualized? Let’s review and practice


  • How could we show a significant relationship between 2 key variables?


  • What is the difference between a linear and exponential function (relationship)?
    • draw a weak exponential relationship between atmopsheric CO2 and ocean pH


  • How could you show the results of an experiment with treatments?


  • Why does both the center and the spread of data matter?
    • draw a comparison of control and warming treatments that are likely biologically different